Edward M. Arnen University of Pittsburgh Pittsburgh 13, Pennsylvania
A Simple, Inexpensive Rotary Film Evaporator
During the past few years the technique of film evaporation has become increasingly popular as a means for the rapid removal of solvent. The simple and inexpensive arrangement shown in the figure may be extemporized rapidly from standard laboratory equipment by replacing the shaft of a hollow-spindle stirrer with a glass tube terminating in a ball-joint a t its upper end and a rubber stopper or standard-taper joint a t the lower end. When lubricated with mineral oil. the ball joint will hold a good water-pump vacuum (10 mm or less) even while being rotated for extended periods. The glass tube to the upper member of the joint should be bent a t an angle so that the condensate will not carry impurities from the suction hose back into the flask. If a hollow-spindle motor is not available, it is usually possible to adapt equipment a t hand, most often by replacing the ordinary solid shaft of an electric stirrer motor by a metal tube of appropriate size. Also, inexpensive, hollow-spindle mounted mandrels are available' and may be used powered through a beltdrive to an ordinary stirrer motor. For multiple evaporations a number of such mandrels may he run in series by belt drives from a single motor, the solvent being
removed through a vacuum manifold attached to the wat,er pump.
As well as being cheap and Y e q . easy to construct, the equipment is simple to clean, has no metal parts that may be attacked by evaporating vapors, and may be taken apart immediately so that the motor is not kept idle for extended periods in an expensive permanent seeup. I n the writer's experience, it is considerably easier to make and holds a steady vacuum more reliably than the device suggested by Greef and Larsem2
' Eberbaoh Corporation, Ann Arbor, Mieh. 2 G (1956).
33, 556 ~ F.,~AND ~ LARSEN, ~ , C. T.,J. CHEM.EDUC.,
Volume 37, Number 5, May. 1960
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247
